Jay Z's ex Roc-a-Fella partner, Damon Dash's is claiming his ex-wife, Rachel Roy, drove drunk with one of the girls, stole diamonds from him, and threatened to cut him with a knife.

Dash made these claims while filing docs demanding full custody of his kids, 15-year old Ava and six year old Tallulah.

In the docs, Dash says Roy threatened his life on several occasions -- once by throwing plates at him, and also by pulling a knife on him. He says sometimes the threats came in front of little Tallulah.

According to TMZ, Dash further claimed in the docs, that Roy stole 2 diamond chains -- worth $10k each -- and a suitcase.

And Dash says he's been blacklisted at Tallulah's fancy L.A. private school, Buckley, because Roy told the school management that he's not allowed to see or pick up their daughter.